METHOD OF BLEACHING SULPHITE CELLULOSE Russian patent published in 2016 - IPC D21C9/16 

FIELD: chemistry.

SUBSTANCE: invention relates to production of sulphite cellulose intended for further chemical processing. Obtaining operational properties of sulphite cellulose required for its further chemical processing is achieved due to ensuring such characteristics as α-cellulose content, weight ratio of lignin, dynamic viscosity, weight ratio of resins and fats, ash content, wettability. For the first stage, i.e. delignification, cellulose mass is used with the concentration of 10 %, added with sulphuric acid, sodium molybdate, hydrogen peroxide. These components are added in the following ratio as per absolutely dry cellulose: H₂SO₄ 0.4-1.5 %; Na₂MoO₄ 0.01-0.5 %; H₂O₂ 2.0-5.5 %. Then the produced mixture is heated up to 60-75 °C, delignification is performed at this temperature for 120-130 min. Washing is performed. Second stage of bleaching, i.e. hot alkaline treatment, is performed, for this purpose the cellulose mass after delignification is brought again to the concentration of 10 %,

EFFECT: added with sodium hydroxide, which concentration is then brought to 1-2 %, the obtained mixture is heated up to temperature of 100-120°, held at this temperature for 120 minutes, and the obtained cellulose is washed.

1 cl, 1 tbl, 6 ex, 1 dwg